UN 1076 — Phosgene

Phosgene, with the UN number 1076, is a colorless gas or fuming liquid below 8°C with a pungent odor of newly mown hay or green corn at low concentrations. It is classified as a DOT class 2 gas and is widely used in the production of pesticides, pharmaceuticals, and other chemicals. First responders may encounter phosgene during transportation accidents, industrial leaks, or fires. The scale of production and transport of phosgene is significant, with thousands of tons being produced and transported annually. As a result, it is essential for first responders to be aware of the hazards associated with phosgene and to have the necessary training and equipment to respond to emergencies involving this substance. Phosgene is also used in the manufacture of dyes, plastics, and other chemicals, which can lead to potential exposure risks for workers and the general public.

Hazard overview: Phosgene is a highly toxic gas that can cause severe irritation to the eyes, skin, and respiratory system, and can be fatal even at low concentrations. The gas is much heavier than air, which can cause it to accumulate in low-lying areas and confined spaces, increasing the risk of exposure. Phosgene can also react slowly with water to form hydrochloric acid and carbon dioxide, which can cause burns and damage to equipment. In the event of a fire, phosgene can produce irritating, corrosive, and toxic gases, including hydrogen chloride and carbon monoxide. The LC50 value for phosgene is 3.3 ppm for a 1-hour exposure, and the IDLH value is 2 ppm. First responders should be aware of these hazards and take necessary precautions to minimize exposure risks.

Response guidance: In the event of a phosgene leak or spill, first responders should isolate the area within a 100m radius in all directions and evacuate the surrounding area, up to 500m daytime and 2000m nighttime for small spills, and up to 7+ km for large spills. The correct suppression agent for phosgene fires is not applicable, as the gas is non-flammable. However, water spray can be used to knock down vapors and prevent the spread of the gas. Decontamination procedures should be followed carefully, and CHEMTREC should be contacted for assistance. First responders should also be aware of the potential for environmental contamination and take steps to mitigate the risks.

Firefighter training notes: First responders should receive training on the hazards associated with phosgene, including its highly toxic effects, and the necessary precautions to minimize exposure risks. They should also be trained on the use of SCBA and full encapsulating suits, as well as decontamination procedures. A common tactical error when responding to a phosgene emergency is to underestimate the risks associated with the gas, which can lead to inadequate PPE and exposure to toxic concentrations. First responders should be aware of the potential for phosgene to accumulate in low-lying areas and confined spaces, and take steps to mitigate these risks.

Regulatory context: Phosgene is classified as a DOT class 2 gas and is subject to the regulations of the Occupational Safety and Health Administration (OSHA). The OSHA PEL for phosgene is 0.1 ppm, and the TLV is 0.01 ppm. Phosgene is also listed on the CERCLA list of hazardous substances, which requires specialized response and cleanup procedures in the event of a spill or leak.

Storage & handling: Phosgene should be stored in a cool, dry, and well-ventilated area, away from incompatible materials such as water and ammonia. The storage container should be designed to withstand the pressure and corrosion effects of the gas, and should be equipped with a safety valve and a pressure gauge. The temperature limit for storage is 8.2°C, and the container should be protected from heat sources and ignition sources.